1. Field of the Invention
This present invention relates to compositions and processes for oil and gas field applications. More specifically, this invention relates to compositions useful for controlling and/or delaying the release of various oil or gas field chemicals, including but not limited to (a) gel-forming or cross-linking agents, (b) scale inhibitors, (c) corrosion inhibitors, (d) inhibitors of asphaltene or wax deposition, (e) hydrogen sulfide scavengers, (f) hydrate inhibitors, (g) breaking agents, and (h) surfactants.
2. Description of Related Art
It is well known to those skilled in the art that certain polymers and other compounds are useful in oil and gas field operations. Such oil and gas field chemicals include (a) gel-forming or cross-linking agents, (b) scale inhibitors, (c) corrosion inhibitors, (d) inhibitors of asphaltene or wax deposition, (e) hydrogen sulfide scavengers, (f) hydrate inhibitors, (g) breaking agents, and (h) surfactants.
In many instances, it is desirable to alter the kinetics of the release of such oil and gas field chemicals, i.e., by providing a composition that provides for controlled or delayed release. For example, U.S. Pat. No. 6,387,986 describes a composition for the delayed release of cross-linking agents by encapsulating the cross-linking agents in a primary emulsion, and then emulsifying the primary emulsion into a second liquid. Despite such advances, there remains a need to develop improved compositions and techniques for the controlled and/or delayed release of oil and gas field chemicals.
In the present invention, a different approach is used for the controlled or delayed release of the oil and gas field chemicals. In the present invention, the oil and gas field chemicals are associated with polyelectrolyte complexes in order to control the release of such chemicals. The resulting nanoparticles also protect the oil and gas field chemicals from hostile down-hole and underground environments so that they can be successfully transported to the target locations underground. To date, polyelectrolytes have largely been used in the pharmaceutical industry to improve drug delivery. See, e.g., Prokop et al., U.S. Pat. No. 6,726,934 entitled Micro-particulate and nano-particulate polymeric delivery system; Tiyaboonchai et al., Formulation and Characterization of Amphotericin B-polyethylenimine-dextran sulfate nanoparticles, Int'l Journal of Pharmaceutics, 90, 902-914 (2001); Tiyaboonchai et al., Insulin containing polyethylenimine-dextran sulfate nanoparticles, Int'l Journal of Pharmaceutics, 225, 139-151 (2003). The present invention is the directed to the use of such polyelectrolyte complexes for applications involving oil and gas field chemicals.